WÄRTSILÄ AXIAL WATERJET SERIES
WATERJET RANGE
With this guide it is possible to make a first jet size
selection and to check weights & dimensions of
jets and possible subsystems. There are two main
waterjet executions available. The pre-assembled
waterjet range and the large jet range have identical
performance properties, as indicated on page 5.
A pre-assembled and pre-aligned jet delivered
with waterjet inlet duct and skid for direct installation
in the ship’s hull. For the pre-assembled execution
all auxiliary systems, such as hydraulic systems and
coolers, are mounted on the assembly and piping
connections are made. These units are available up
to approx. 4500 kW and fit in a standard 20 or 40
foot sea container.
For large jets the inlet duct is designed by
Wärtsilä and built by the shipyard as part of the ship
construction. Auxiliary systems for the large jet range
can be selected with this guide, based on the vessel
design details. The largest waterjet in our order book
is a 26,000 kW LJX2180 unit. Our design capability
goes up to 50 MW.
2
WÄRTSILÄ AXIAL JET TECHNOLOGY
Wärtsilä axial waterjets are a line of
single stage, compact high performance
waterjets combining mixed flow
properties with an axial build. The result
is a much reduced vessel transom
occupation with highly increased waterjet
cavitation margins for optimum vessel
operating flexibility. The reduced transom
occupation is achieved without reduction
of the inlet duct diameter or reduction
of the waterjet pump size in order to
maintain maximum efficiency for lowest
fuel burn.
AVERAGE 25% REDUCED
TRANSOM OCCUPATION
Jet sizes are indicated by the front side
diameter of the impeller seat ring. Unlike
a non-axial design, the Wärtsilä axial
design waterjet does not expand in radial
direction downstream. The flow through
the jets is directed through the pump
over the most efficient path, while at the
same time the transom mounting flange
diameter is reduced. This will allow much
easier fitting of the jet in the available
space either in width or height. For naval
architects it will deliver the possibility to
apply a larger power density onto narrower
hulls for achieving top vessel performance.
AVERAGE 10% HIGHER SHAFT SPEED
= 10% LESS TORQUE
Compared with non-axial designs, the
shaft speed of the impeller is on average
10% higher whilst the impeller tip speed
is still lower. This is achieved by the
impeller shape creating a large amount
of blade surface area within small radial
dimensions. The low impeller tip speeds
avoid sand erosion, making the axial jet
ideal for shallow water operations, such as
landing craft. At full manoeuvring power
Diameter used for
type designation
Diameter used for
type designation
INLS system for the US Navy equipped with custom designed jets for thrust in all
directions (360° revolving jet nozzle ﬁtted)
the impeller tip speed is maximum 30 m/s.
The lower torque – a direct result of the
higher shaft speeds with low tip speeds –
can yield both weight and cost savings for
couplings in intermediate shaft lines, for
shafts in general and gearboxes.
UP TO 10% LOWER WEIGHT
The reduced transom size not only results
in reduced dimensions, but also gives the
installation a substantially lower weight.
Combined with our welded jet construction
this permits further weight optimizations
and savings that can be as high as 15%
compared to non-axial jet designs. Since
(waterjet) weight at the very end of the vessel
is usually difficult to compensate elsewhere
in the ship, jet weight savings can result in
improved trim of the vessel. Weight savings
also increase the payload within the same
vessel design.
LARGE MARGINS FOR OPERATING
FLEXIBILITY AND MANOEUVRING
The pump cavitation margins are increased by
at least 35%. Thanks to this larger cavitation
margin and the lower impeller tip speed,
more power can be allowed onto the pump
during manoeuvring, resulting in a 15% higher
manoeuvring thrust and faster response to
acceleration. Also more power will be available
to overcome changing operating conditions,
such as increased vessel resistance due to
shallow water effects. Furthermore, with the
additional cavitation margin, operation with
a reduced number of shaft lines is possible
at higher loads of the remaining engines,
improving operating flexibility.
BLACK SMOKE REDUCTION
MARGINAL INCREASE IN POWER
ABSORPTION AT MANOEUVRING
During manoeuvring the diesel engine operates
in its critical zone while in this area waterjets
tend to absorb increased power for lower
impeller speeds. The result can be a high
load for the engine, causing smoke and an
increased thermal load. Thanks to Wärtsilä
axial jet series this unwanted increase in power
absorption is up to 70% lower than that of
competing non-axial designs.
DESIGN LAYOUTS
All jet designs are available in a steering/
reversing (SR), reversing only (R), steering
only (S) and booster execution (B). For jet
sizes in between approx. 1000–4500 kW,
pre-assembled easy to install packages (SRF
executions) are available. On request we offer
solutions for special applications e.g. thrust
in all 360° directions. The key benefits of the
axial technology are valid for all executions.
3
Machinery controls box with factory
settings made ahead of sea-trials
Cylinders and thrust bearing inboard resulting
in full absence of oil lubricated or oil containing
parts outboard of the vessel
All piping connected, just one cooling water
connection to be made by the shipyard
Weld-in skid manufactured in the
same material as the hull
Unique compact high performance
steering & reversing assembly
Hull customised inlet duct in Wärtsilä supply for
top performance and shipyard risk reduction
PRE-ASSEMBLED WATERJET PACKAGES
THE WATERJET PUMP
For all Wärtsilä waterjets – large units or
pre-assembled units – exactly the same pump
is used and the same hydrodynamic design
process is applied. Pump impeller, stator
section and shaft are all manufactured of the
same high quality materials for continued top
performance long after Newbuild trials.
STANDARDISED BUT NOT COMPROMISED
HIGH PERFORMANCE WITHIN EASY REACH
Every Wärtsilä pre-assembled waterjet
package delivers the customised performance
of large jets into the market of pre-assembled
jet packages up to 4500 kW. The inlet duct
of the pre-assembled waterjet package is
optimized for hull shape & operational profile.
Modern and cost efficient manufacturing
techniques accurately transfer the
Computational Fluid Dynamics designed
shape from the screen to the shop floor. After
construction the inlet duct is seamlessly
integrated in the waterjet assembly that is
4
shipped as one plug-and-play unit for instant
installation by the ship yard.
STEERING AND REVERSING
COMPACT AND FAST
In the market of pre-assembled waterjet
packages, the steering and reversing assembly
is unique in its shape and dimensions.
Deviating from the market standard, our
assembly fits well within the waterjet stator
transom mounting flange, providing optimum
positioning of multiple jets in the available
transom width. Also the clearance required
above the jet is small and a (swimming)
platform is easy positioned above the jets.
MAINTENANCE OPTIMIZED
All cylinders are positioned inboard as well
as the waterjet thrust bearing. Apart from the
operating reliability delivered it also provides
easy access for maintenance without the need
for dry-docking. There are no oil lubricated or
oil containing parts outboard the transom.
QUALITY MATERIALS
FOR CONTINUED HIGH PERFORMANCE
High performance is one of the key features
of the Wärtsilä axial jet series. However,
an incorrect material selection can slowly
degrade the performance of a waterjet in the
years after sea trials. For that reason Wärtsilä
avoided aluminium as construction material
for the waterjet stator bowl. The stator bowl
plays a very critical role in the jet efficiency
and the stator blade profile must remain in
top condition as originally designed. It blocks
a slow efficiency decrease over time as result
of stator blade flow sheering or unwanted
rotation of the flow. The Wärtsilä stator bowl
is therefore constructed of a high grade
stainless steel as common for our large jet
series. In addition to better performance, the
maintenance requirement of the high grade
stainless steel stator is minimal.
WÄRTSILÄ 450–810 SIZES
4500
810 size
DIMENSION TABLE FOR PRE-ASSEMBLED SRF PACKAGES
Waterjet size
4000
510
720 size
Engine power (BkW)
3500
3000
640 size
2500
570 size
2000
510 size
1500
450 size
510 size
450 size
1000
500
15
20
25
30
35
Vessel speed (knots)
40
45
WÄRTSILÄ 910–1400 SIZES
14 000
1400 size
13 000
Engine power (BkW)
12 000
11 000
1300 size
10 000
1200 size
640
720
810
1400
1550
1750
1950
2200
(1500*) (1700*) (1900*) (2100*) (2400*)
A
mm
B
mm
1000
1100
1200
1350
1550
C
mm
2300
2600
2800
3100
3600
D
mm
3000
3400
3800
4200
4800
E
mm
1100
1200
1400
1500
1700
F
mm
510
570
640
720
810
Weight steering**
kg
1450
1800
2450
3000
4000
Weight booster
kg
1050
1300
1800
2250
3000
Entrained water
l
400
600
800
1150
1650
* When in reverse. ** Without oil and entrained water.
C
9000
A
1100 size
8000
570
F
7000
1000 size
910 size
6000
E
5000
910 size
4000
B
3000
2000
D
15
20
25
30
35
Vessel speed (knots)
40
45
Engine power (BkW)
WÄRTSILÄ 1500–2180 SIZES
2180 size
32 000
30 000
28 000
26 000
24 000
22 000
20 000
18 000
16 000
14 000
12 000
10 000
8000
6000
15
2020 size
AXIAL SERIES WATERJETS
Weight & dimensions of pre-assembled SRF waterjet packages
1880 size
1750 size
1620 size
1500 size
20
25
30
35
Vessel speed (knots)
40
45
WATERJET SIZE SELECTION
The graphs above indicate the jet size required based on the relation
between the engine power and the design speed of the vessel. For
instance a ship with four 1250 kW engines and a corresponding
vessel speed of 33 knots will need four 510 size waterjets. A ship
with a design speed of 40 knots at 1250 kW power can use 450 size
waterjets. The correct jet size is thus indicated by the line above the
intersection of the power and the corresponding vessel speed (see
examples in graphs above).
Please contact us for an optimized jet selection based on specific
vessel design parameters and operating profile, or for details on
waterjets above 50 knots or 30 000 kW. DXF/DWG format general
arrangement drawings of the most often used sizes are available.
Waterjet Outboard
size
length mm
Inboard
length
mm 1)
Transom
flange
diameter
mm
Weight
Weight
steering kg Booster kg
910
2300
4050
1165
3200
2250
1000
2500
4400
1280
4200
2900
1100
2800
4750
1405
5300
3700
1200
3000
5300
1535
7350
5300
1300
3250
5650
1665
8950
6250
1400
3500
6050
1790
11 100
7700
1500
3750
6550
1920
14 250
10 050
1620
4050
7000
2075
17 250
12 000
1750
4350
7500
2240
21 200
15 050
1880
4650
8050
2405
28 950
20 600
2020
5000
8550
2585
34 350
24 150
Note
1) Inboard length may vary depending on the optimized shape of the inlet duct.
Outboard length
Inboard length
5
LARGE WATERJETS
LARGE MARGINS
FOR OPERATING FLEXIBILITY
Our large axial jets have set a standard in the
past years. Introduced in 2006 and selected
for many leading large vessel applications,
such as the US Navy JHSV and LCS programs,
Incat catamarans, and leading superyacht
applications. In addition to our axial design a
non-axial design is also available for vessels
requiring extremely high speeds above 55
knots up to speeds above 70 knots.
The information on the following pages is
for the large jet range only. Wärtsilä preassembled packages come fully assembled as
one package for direct installation in the ship
(see page 5).
JET HYDRAULIC SYSTEMS
Each steering and reversing waterjet requires
a hydraulic power pack (HPP) for steering
control and reversing actions. Two stainless
steel hydraulic cylinders are used to pivot
the steering bucket port and starboard, and
one central hydraulic cylinder to activate
the reversing plate up and down. Hydraulic
cylinders are fitted with integrated feedback
sensors linked to the electronic jet control
system for feedback and indication. The
control of each steering and reversing waterjet
installed is independent and failure in one
hydraulic system will not affect the other jets.
STANDARD HYDRAULIC POWER PACK (HPP)
AND LUBRICATION OIL PACK (LOP)
The hydraulic power pack for control of jet
steering and jet reversing movements, and the
lubrication unit for the waterjet thrust bearing,
are combined in a single tank with two
compartments for efficient installation at the
yard site. The hydraulic and lubrication loops
6
SR-series. The most compact waterjet available for
large fast vessels
are fully separated to avoid any contamination
between hydraulic and lubrication oil. The main
hydraulic pump of the standard HPP is driven
by a Power Take Off (PTO) from the gearbox or
from the engine. In addition, an electric driven
pump is installed on the oil tank. The electric
pump is used to control the jet movements
with a reduced capacity when the main PTO
pump is not available.
The hydraulic power pack is standard equipped
with:
z 1 x steel tank with two separated
compartments, hydraulic and lubrication
z 1 x startup backup, cooling pump, vertically
mounted
z Double gear pump PGP511 series
z E-motor
z Bell-housing and flexible coupling between
E-motor and gear pump
z 1 x steel manifold with valves/functions
according to hydraulic diagram (next page)
z Load sense circuit for PTO pump and
“startup flow” control
z Filter by-pass alarm
z Steering function:
1 x proportional directional control valve
1 x flow/pressure compensator
2 x load holding valve
z Reverse function:
1 x proportional directional control valve
1 x flow/pressure compensator
1 x load holding valve
z Flushing function for PTO pump
1 x flushing connection with flow control
valve
z 1 x oil–sea water cooler with Thermo valve
z 1 x return filter mounted on the tank-cover
z 1 x temperature gauge
z 1 x dip-stick
z
z
z
z
z
z
1 x Thermo switch
2 x level switch; low and too low
1 x air breather with steel cap
1 x gate valve
1 x drain valve
1 x junction box and wiring to all
components
The lubrication section is standard equipped
with:
z 1 x line mounted “medium pressure” filter
with clogged filter alarm
z 1 x filter by-pass function – 2-way ballvalve with non-return valves – for filter
exchange
z 1 x oil–sea water cooler
z 1 x temperature gauge
z 1 x dip-stick
z 1 x pressure switch
z 1 x pressure gauge
z 1 x level switch
z 1 x air breather with steel cap
z 1 x drain valve
z 2 x differential pressure switch
NOTE: INSTALLATION DISTANCES
Long distances between HPP and waterjet and
between HPP and the PTO connection for the
hydraulic pump should be avoided. Pressure
losses will occur in the piping if connections
are too far apart and the jet steering/reversing
performance could deteriorate. Oil filled piping
running through the vessel over long distances
also increases installation weight. If such
distances cannot be avoided, we can supply
full electric driven power packs with the pump
directly mounted on the HPP tank, eliminating
all pressure and suction piping between
pump and HPP. Please contact us for more
information.
Forward thrust
Reverse thrust
Zero thrust
Steering
Standard power pack arrangement.
7
Settling time steer2
sec
Settling time rev3
sec
E-motor power
kW
Cool cap. hydr
kW
Cool cap. lubr.
kW
21.17 18.91 40.08
8
8
3
5.12
5.35
1000
23.30 25.16 48.46
8
8
3
6.19
5.27
1100
25.60
35.71 61.31
8
8
4
7.83
5.27
1200
28.32 39.16 67.48
10
10
4
8.62
6.95
1300
37.70 42.39 80.09
10
10
5.5
10.23
6.94
1400
40.57 59.59 100.16
10
10
5.5
12.80
6.99
1500
52.39
63.94 116.32
10
10
7.5
14.86
9.08
1620
60.70 72.78 133.48
12
12
7.5
17.06
9.25
1750
65.58 97.08 162.55
12
12
11
20.78
9.51
1880
88.06 104.30 192.36
12
12
11
24.58 14.03
Max. flow total1
l/min
Max. steer flow
l/min
910
Max. rev flow
l/min
Jet size
DESIGN DATA FOR HYDRAULIC SYSTEM UNITS
1) Max flow total – represents the flow required for a combined steering and reversing demand that
results in the settling times as given in the table. For a 1400 size jet the flow of 100.16 dm3/min will
thus move the jet over the full steering range and the full reverse range in 10 seconds.
2) Settling time steering – time required for a full 60 degree steering movement.
3) Settling time reversing – time required for a full movement from either full ahead to full astern or v.v.
Pump Displ.
type cc/rev
1
2
3
4
5
6
7
8
9
16.2
25.2
40.5
54
67.5
94.5
130.5
162
243
Max.
rpm
1800
1800
1800
1800
1800
2300
2200
2200
1800
Max.
press.
bar
280
280
280
280
280
320
320
350
350
Rot
Shaft
Flange
Weight
kg
CCW
CCW
CCW
CCW
CCW
CCW
CCW
CCW
CCW
SAE-A
SAE-B
SAE-B
SAE-C
SAE-C
SAE-C-C
SAE-D
SAE F
SAE F
82-2 (A)
101-2 (B)
101-2 (B)
127-2 (C)
127-2 (C)
127-2 (C)
127-2 (C)
SAE 4 hole
SAE 4 hole
14
18
18
29
30
63
78
90
172
LOAD SENSE VARIABLE DISPLACEMENT
PUMP FOR DIRECT MOUNTING ON THE
GEARBOX PTO
The selection of a suitable gearbox PTO can be
made with the tables above. For instance the
jet size that you have selected for your vessel
with the jet selection graphs on page 5 is a
1400 size jet. The first table above indicates
that the flow for a combined steering and
reversing movement is 100.16 dm3/min in
order to achieve settling times of 10 seconds.
If the engine runs at 600 rpm at idle, and
the step up ratio of the PTO on the primary
side of the gearbox is 1, then the pump
capacity according to the second table above
has to be 100,160/600 = 166.9 cc/rev
(size 9). If the step up ratio of the PTO at the
primary side of the gearbox is 2, then a pump
capacity of 83.47 cc/rev (size 6) is sufficient.
TYPICAL REFERENCES/APPLICATIONS
Waterjets propulsion is the most successful
and efficient method of propulsion for highspeed applications. The advantages are
8
US NAVY, LITTORAL COMBAT SHIP
LCS-2 USS INDEPENDENCE
2 x LJ150E waterjets for the wing propulsion lines
2 x LJ160E waterjets for the centre propulsion lines
not only higher efficiency, but also lower
vessel resistance due to the absence of
underwater appendages like shafts, rudders
and shaft struts. The absence of parts below
the waterline also makes waterjets an ideal
solution for shallow water operation.
With excellent manoeuvrability at all vessel
speeds, waterjets deliver fast turn-around
times for all applications. With catamarans it
is usually possible to achieve pure sideways
movement and 360 degree turning without a
bow thruster.
FAST FERRY
Waterjets developed fast together with the rise
of the fast ferry industry. With jets delivered to
all the main builders of car/pax ferries, there is
a broad experience for these systems.
FAST NAVAL CRASH STOP SYSTEM
Waterjets do not require reversal of the rotation
direction to generate astern thrust. A bucket
redirects the flow from the nozzle, generating
full astern thrust generally within 8–10
seconds after the command was given on the
bridge. With special, fast crash stop jets the
time to full crash stop thrust can be shortened
to less than 3 seconds. The example to the
right illustrates the crash stop action of such
an installation, redirecting more than 40.000
litres of 120 km/h sea water in an instant,
while the gas turbine driving the jet keeps
turning at constant high load throughout the
crash stop operation.
HYBRID OR WARP SYSTEMS
Unique to Wärtsilä is the delivery of various
hybrid or Waterjet And Refined Propeller
(WARP) systems. These systems combine
controllable pitch propellers with a waterjet.
The benefit is that the largest parts of the total
installed vessel power can be absorbed by the
waterjet. Despite the high amount of power
the dimensions of the jet remain relatively
small due to the high allowed power density
compared to a propeller. With the jet taking
most of the total vessel power, the propellers
can remain small in diameter as well limiting
Crash stop action of LJ210E jet in a 86 m
corvette driven by one 20 MW gas turbine
and approx. 11,000 kW Diesel power.
Copyright Austal Australia 2009
Incat 112 m fast ferry equipped with four 1500SRi jets each driven by 9000 kW
Diesel engine (4 vessels delivered).
the draft of the vessel. The result is a very attractive
operational profile. The propellers are fully optimized
for lower cruising speeds delivering optimum
efficiency with low noise and vibrations. At the
same time the combination of the waterjet and the
propellers still gives access to higher speeds when
required. Hybrid systems were delivered for various
yachts with total vessel power up to 32 MW and for
Navy vessels up to 28 MW.
SHOCK REQUIREMENTS
FOR JETS IN NAVAL USE
Several waterjet installations have been supplied
with shock requirements proven by calculations. The
main changes required in case of shock are shock
mounts for equipment such as the hydraulic power
packs and oil lubrications sets, and strengthening
of the thrust bearing. Due to the inboard position of
the bearing that is relatively easy. The housing of the
bearing – standard of aluminium to minimize weight
– is replaced with a steel housing and if required the
bearing can be somewhat oversized. Please contact
us to learn the possibilities and required actions
based on your project details.
Hybrid or WARP system.
9
Q&A
AXIAL VS. NON AXIAL
WHAT IS THE DIFFERENCE BETWEEN AN
AXIAL AND NON-AXIAL WATERJET? The
waterjet principle (see also under jet working
principle) is based on a pump. Pump types can
be grouped from pure axial to radial pumps.
A pure axial pump will deliver a high flow at a
low pressure. A pure radial pump will generate
a low flow at a high pressure. For a high thrust
output a waterjet needs to generate both a
high flow through the jet system and a high
pressure, requiring a jet pump with so called
“mixed flow properties”. The unique feature of
the Wärtsilä axial flow waterjet is that it has
the mixed flow properties required, but delivers
it in a pure axial geometry. This results in a
substantial advantage as the water follows the
optimum flow path straight through the pump
instead of partly travelling in radial direction
before exiting at the nozzle.
WHAT IS THE DISADVANTAGE/LIMITATION
OF AN AXIAL JET? Axial jets are primarily
focused on applications with maximum speeds
up to 50 – 55 knots. Above that the axial jet
should not be used and a more radial shaped,
mixed flow pump will give better results (see
also section above). For these extremely high
speed applications, we offer our E-series
waterjets.
WHAT ARE THE BENEFITS OF AN AXIAL
JET? Compact, high efficiency, low weight,
more cavitation margin, higher shaft speed
reducing torque, low forces transferred to the
ship construction.
HYDRAULIC SYSTEMS
WHAT IS THE DIFFERENCE BETWEEN
ELECTRIC AND PTO DRIVEN POWERPACKS?
For an electrically driven powerpack all power
for displacing the oil volume is delivered by
an electric power source. The pump for a
PTO driven powerpack is driven by a Power
Take Off of the gearbox or engine. For such a
powerpack normally an electric backup from an
electrically driven pump with reduced capacity
is installed (see page 6). The big advantage of
an electrically driven powerpack is the absence
of long suction and pressure lines between the
pump and the oil tank, since the full electric
driven pump is mounted directly on top of
the tank. This decreases installation work
10
and minimizes pressure losses in suction and
pressure lines. Further a full electrically driven
powerpack is independent from the engine
speed. At low speed and idle maneuvering
conditions the available speed from the engine
for driving the HPP PTO pump is low, while
the request for hydraulic power during vessel
maneuvering is high. An electrically driven
pump is thus smaller in size than a PTO driven
pump.
DO PTO POWERPACKS HAVE A BACKUP
FACILITY? Yes, on a HPP with a PTO (Power
Take Off) driven pump a second electrically
driven pump is mounted directly on the HPP
oil tank. However, the backup has a limited
capacity (see page 7). This means that
response times will be lower in HPP backup
mode.
CAN THE POWERPACK BE PLACED IN
ANY LOCATION? It is advised to place the
powerpack as close as possible to the jet
steering assembly, as that is the location
where the hydraulic power has to be delivered.
In case of a powerpack with a PTO driven
pump the distance to the PTO also has to be
taken into account, to avoid too high losses in
piping to that end.
CAN THE PTO BE PLACED IN ANY
LOCATION? The PTO driving the hydraulic
pump is normally placed on the primary side
of the gearbox. In this case it is possible to
put the jets into zero thrust position while
the engine is running, before jet clutch in.
Placement on the secondary side is possible,
but electric power will have to be available to
control the jet before clutch in with an electric
backup motor.
WILL THE POWERPACK STILL WORK IF
THE ENGINE ROOM IS FLOODED? Standard
powerpacks will malfunction due to water
ingress through the breather and other
parts. To avoid malfunction due to flooding
of compartments it is advised to place the
powerpack one deck above compartments
that can possibly be flooded in emergency
situations. Measures can be taken to avoid
malfunction due to flooding, but the costs –
depending on the exact demands – are high
without exception.
WHAT DETERMINES THE DIMENSIONS OF
THE POWERPACK? Jet size, required settling
times and maximum roll of the vessel.
WHAT IS THE ADVANTAGE OF INBOARD
HYDRAULICS? An inboard hydraulic system
brings all hydraulic cylinders and hoses inboard
of the vessel in the jet room. This reduces
maintenance in general, especially when the risk
for marine growth is high. Specific advantages
are operation in ice conditions or waters with
high debris content. Furthermore, vulnerable
marine environments can benefit as there are no
systems containing oil outboard the transom in
combination with our inboard thrust bearing and
outboard water lubricated bearing.
JET – ENGINE MATCHING
CAN YOU ADJUST THE WATERJET SHAFT
SPEED TO SUIT A GEAR RATIO? Yes, by
varying the jet size for a constant engine power.
However, by purely selecting the jet size to suit
a gear ratio, the jet will become larger than
strictly required for your operation. The gearbox
manufacturer should thus offer suitable gear
ratios to ensure the best performance of the
waterjet system.
DOES WÄRTSILÄ DETERMINE THE GEAR
RATIO? With the engine performance diagram,
Wärtsilä selects the best ratio out of the gear
ratios offered by the gearbox manufacturer.
In case a proper ratio is not available, a
different gearbox has to be selected to avoid
underperformance of the waterjet.
WHAT HAPPENS IF THE JET AND ENGINE
ARE NOT PROPERLY MATCHED? If the gear
reduction ratio is too low the waterjet will rotate
faster than optimal, delivering more thrust but
possibly overloading the engine. If the reduction
ratio is too high, the jet will not turn fast enough
and underperform.
IS SEA MARGIN REQUIRED FOR A JET? No,
sea margin is not required. Compared to a fixed
pitch propeller there are two main differences.
Because of the jet inlet duct the jet impeller is
not directly inside the hull wake flow and the jet
impeller operates in a “protected” environment
created by the Wärtsilä designed inlet duct.
Further, in deviation with an FPP, a jet is a pump,
and thus a different type of machinery (turbo
machinery) with a relatively flat power absorption
curve is required.
WHAT IS THE SHAFT SPEED OF A WATERJET?
The shaft speed depends on the jet size and the
power applied. A small jet at high power can run
at 2000 rpm, a large one at 200 rpm.
WHAT IS THE STANDARD DIRECTION OF
ROTATION FOR A JET? Clockwise when facing
forward from aft. A different direction is possible,
but is considered a custom design with longer
delivery time and higher initial costs.
vessel baseline in the transom, reducing vessel
JET MAINTENANCE
both high and low vessel speeds.
CAN YOU DESCRIBE THE MAINTENANCE
REQUIRED FOR A WATERJET? We offer
standard maintenance packages for every
mechanical job on the waterjet. The standard
packages contain all parts and consumables
required for a particular job. Standard
maintenance intervals are every 2.5 years and
every 5 years. Five years is normally a class
required docking interval. Maintenance strongly
depends on the intensity of the service and
local conditions.
FOR WHICH APPLICATIONS HAS WÄRTSILÄ
JET OFFER
WHAT INFORMATION DOES WÄRTSILÄ NEED
FOR MAKING A WATERJET SELECTION
AND OFFER? As a minimum the waterline
length of the hull, the number of shaft lines
and the relation between the ship design
speed and the engine power; e.g. 40 knots
at 4 x 7200 kW with a waterline length of
75 meter. If the relation of speed and engine
power is not known, we can make a rough
estimate based on the displacement of the
vessel. Additional information useful to further
sharpen the jet selection is full resistance data
of the hull including various displacements, the
ship operating profile and any specific design
requirements.
WHY USE WATERJETS?
HOW DO I KNOW IF I SHOULD USE
WATERJETS OR PROPELLERS? That should
be investigated case by case. In general
waterjets are not used for ships with design
speeds below 30 knots, unless the vessel
is in special service, such as shallow water
operation.
The advantage of jets over propellers is their
ability to absorb high input powers on a small
diameter, reducing the size of the installation.
Further, the steering is integrated in the
jets and rudders are thus not required. The
absence of rudders and other appendages,
such as shaft struts, will substantially reduce
the resistance of the hull at high speed. Other
reasons for using waterjets can be shallow
water access, as the jet unit sits above the
draft and avoiding damage from grounding.
Good maneuverability can also be a reason to
select jets as propulsion units. There is always
a relatively high flow leaving the jet nozzle at
DELIVERED WATERJETS? For everything
from slow 10 knot applications requiring
high maneuverability to high speed and high
powered 70 knot applications. Further several
hybrid (see also next question) solutions, as
well as various custom solutions for special
vessels, have been delivered.
CAN WATERJETS AND PROPELLERS BE
COMBINED? is possible for some applications,
Wärtsilä calls that the Waterjet And Refined
Propeller (WARP) systems. Usually these
applications have top design speeds around
PRIMING, WATER COVERAGE
30 knots and an operating profile requiring
frequent operation around 20 knots and
occasional operation around 30 knots. These
systems with two wing propellers and a central
booster jet operate on propellers only for the
speed around 20 knots, and on combined
propellers and jet for reaching the top speed.
The main advantage is smaller propellers
than on an “all propeller 30 knots ship”, as
the propellers are optimized for the power
>Idle
requirements around 20 knots. These hybrid
systems can thus be very attractive as they
combine the best of both worlds for ships
around 30 knots.
JET OPERATION
WILL THE JET START ITSELF? This depends
on shaft height and ship speed. At a ship
speed of 0 knots and with the waterline not
lower than on or just below the jet shaft centre
Above idle
line, the jet will always start (prime) at normal
idle engine speed. If the water level drops far
below the impeller shaft, priming will slowly
become more difficult and higher starting shaft
speeds will be required for priming the pump.
When the ship makes speed, starting inactive
jet propulsion line will become easier even if
the waterline is far below the jet impeller shaft.
Due to the ship speed water will be forced into
the jet inlet duct.
High rpm
11
SERVICES
Several customers have recognized us as
their preferred service supplier to ensure the
availability and cost-efficient operation of their
installations. They benefit from having their
entire power system fully serviced by one
global supplier. Wärtsilä Services provides full
service throughout the product lifecycle for
both marine and power plant customers, and is
constantly developing its network worldwide.
Additionally, we are continually
broadening our range of services by adding
valuable products and specialist services
to our portfolio. In this way we also support
equipment onboard your vessel or at your
installation and in our numerous workshops
around the globe and in key ports, regardless
of your equipment make.
We offer lifecycle efficiency solutions in the
following services product lines:
z Engine Services
z Propulsion Services
z Electrical & Automation Services
z Boiler Services
z Operations & Management Services
z Training Services
z Environmental Services
These services cover everything from
basic support with parts, field service and
technical support to service agreements
and condition based maintenance; from
installation and commissioning, performance
optimization, including upgrades and
conversions, to environmental solutions,
technical information and online support.
The choice available to you extends from
parts and maintenance services to a variety
of comprehensive, customized long-term
service agreements, including performance
and operations & management agreements.
Our Services organization currently features
more than 11,000 dedicated professionals
in 70 countries.
Wärtsilä adds value to your business
at every stage in the lifecycle of your
installations. With us as your service partner,
you receive many measurable benefits such
as availability and performance, productivity
gains and cost benefits. Above all, peace of
mind in the knowledge that your installation
is being serviced by the most experienced
partner you could have – Wärtsilä.
SUPPORT
FROM YOUR
LOCAL OFFICE
For a final jet selection you are always
welcome to consult a local Wärtsilä office. In
cooperation with the centre of excellence for jet
propulsion they will optimize the selection and
jet performance based on the requirements of
your ship design, hull parameters and/or ship
operating profile.
The addresses of our local offices worldwide
can be found on www.wartsila.com,
or you can contact one of the below offices for
specific applications.
Wärtsilä-Lips Inc.
3617 Koppens Way
Chesapeake Virginia 23323, USA
Tel. +1 757 558 3625
Wärtsilä Defence
3 Boulevard de La Loire
Nantes 44275, France
Tel. +33 240 411 602
Wärtsilä Netherlands
Lipsstraat 52
5151RP Drunen, The Netherlands
Tel. +31 416 388 208
marine and energy markets. By emphasising technological innovation
and total efficiency, Wärtsilä maximises the environmental and economic
performance of the vessels and power plants of its customers. Wärtsilä
is listed on the NASDAQ OMX Helsinki, Finland.
WÄRTSILÄ® is a registered trademark. Copyright © 2011 Wärtsilä Corporation.
01.2010 / Bock´s Office /
Wärtsilä is a global leader in complete lifecycle power solutions for the